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Grubs in your lawn?

a guide for lawn care professionals and homeowners

The Grub-damaged Lawn

Severe grub damage in a lawn appears as large, irregular sections of brown turf that detach from the soil without effort. Unlike turf damaged by drought or excessive fertilizer, the turf peels away like a carpet being rolled up, because most of the roots are gone.

For most of the year, however, grubs are out of sight and out of mind. They feed on grass roots in your lawn and are usually noticed only when dead and damaged areas appear.

Find Your Problem Areas

You can prevent losses by locating high grub populations before they cause damage.

When to sample

Seek out grubs in early August on Long Island and in mid-August upstate. Sampling early in a grub’s life cycle means that you’ll catch grubs while they are small and less capable of seriously damaging your lawn.

Where to sample

map of home and yard
Draw a simple map and mark sampling sites. Illustration by K. English, NYS IPM.

Begin by sketching a simple map of your property. Now think of areas that are important to you from a visual or aesthetic standpoint. The front lawn, where visitors enter? Near the back patio? Mark these high-priority areas with Xs that translate to about 10 feet apart. These will be your sampling sites. Consider areas with a history of grub damage and mark these areas, too. Mark low-priority areas with Xs every 20–30 feet. You probably won’t need to sample or treat remaining areas.

Mount your map on a clipboard, grab a full watering can, a piece of cardboard, and either a cup cutter, bulb planter or a shovel, and go to one of the sampling sites marked on your map.

How to sample

Method 1: bulb planter or cup cutter

man using cup cutter dirt on cardboard
Sampling with the cup-cutter (bulb-planter) method. Photos: J. Grant, NYSIPM

Use a bulb planter or a cup cutter (golf course tool) to remove a core of soil and grass. Examine the contents on a piece of cardboard. The area is approximately 1/10 of a square foot of sod. Jot down the number of grubs on your map, then multiply it by 10 for the number of grubs per square foot. Replace the soil and sod, and water thoroughly.

Method 2: shovel

If you have time to take only a few samples, try this method. Using a garden shovel or spade, cut three sides of a 12-inch square. Grab a hold of the open edges and peel back the turf like a carpet, towards the attached side. Look for c-shaped grubs on the newly-exposed soil and under the sod mat. Count them and make a note on your map. Replace the sod, water thoroughly, then move to your next sampling site.

Scouting for grubs helps you decide whether to treat—but first, watch for natural controls.